1. Field of the Invention
The present invention relates to an access control apparatus and access control method for connecting unspecified user terminals to a public network via a leased circuit installed by a service provider and, more particularly, to an access control apparatus and access control method which set a time limit for access to a public network.
2. Description of the Prior Art
An access control apparatus has conventionally been utilized to connect unspecified user terminals to a public network via a leased circuit installed by a service provider. The access control apparatus assigns an address to a user terminal and grants an address-assigned user terminal access to a public network.
The access control apparatus controls the number of user terminals who are permitted to access a public network by limiting the number of addresses to be assigned to user terminals or setting an expiration date for use for an address to be assigned.
When the number of addresses to be assigned to user terminals is limited, a user terminal can keep accessing a public network without any time limit on the user terminal which has acquired an address once.
When a time limit is set for an address to be assigned, another address is reacquired after an expiration date for use of the address. The same user terminal can access a public network without any time limit.
If a specific user keeps accessing a public network by using a specific user terminal, another user cannot use this user terminal or cannot access a public network even with another user terminal.
A conventional technique of assigning an address to a terminal apparatus is “Address Assignment Apparatus and Method, Address Assignment Program, and Storage Medium Which Stores Address Assignment Program” disclosed in Japanese Patent Application No. 2002-374280 (patent reference 1). According to the invention disclosed in patent reference 1, a network address is assigned on the basis of attribute information acquired from a user terminal by an address assignment apparatus.
The invention disclosed in patent reference 1 aims to assign different addresses to user terminals on the basis of attribute information and permit connection in a form corresponding to an assigned address. The invention does not try to prevent continuous connection of a user terminal to a network.
There have not been proposed any access limitation apparatus and access control method which temporarily limit connection to a public network from a user terminal which is connected to the public network via a leased circuit.